Underwater breathing apparatus



UNDERWATER BREATHING APPARATUS Filed Aug. 31, 1956 Q 6' INVENTOR. F 6 '3F 051055 LM/wsh' BY m M M Anne/v96 fine Patented Feb. 26, 1%62 3,921,839UNBER NAEER BREATHNG APPARATUS De Loss L. Marsh, 1453 Revere Ave,Hayward, Calif. Filed Aug. 31, 1956, Ser. No. 607,406 6 (Ziaims. (Cl.128-142) This invention relates to a breathing apparatus. Morespecifically, this invention relates to a breathing apparatus of thesemiclosed circuit type designed for use in skin diving, such asapparatus described in my copending application, Serial No. 512,223, nowPatent No. 2,900,977.

Several forms of underwater breathing apparatus, capable of beingcarried by a diver, have been proposed, the forms being generallyclassifiable as of the open circuit type and of the closed circuit type.

The open circuit type of underwater breathing apparatus is that type inwhich air, or oxygen mixed with an inert gas, is stored in cylindersunder high pressure (ap proximately 2000 psi.) the cylinders beingfastened to the diver. This high pressure air is reduced to anintermediate pressure range (approximately 55-125 psi.) by a first stagepressure reduction valve. The air is obtained by the diver on inhalationthrough a second demand type pressure reduction valve actuated byrespiratory action, with the pressure of the air delivered to the diverbeing equal to'the existing water pressure at any depth. The entireexhalation of the diver is discharged through his nose and mouth intothe water.

The open circuit type has the distinct advantage that it is completelyautomatic, in that the air supplied to the diver is automaticallycompensated for pressure difference as the diver rises or descends inthe Water. Furthermore, by using air alone, the diver may descend todepths up to 300 feet without danger of oxygen poisoning.

The biggest disadvantage of the open circuit type is its inefliciency.It is well known that the body uses only about one-fifth of the oxygentaken into the lungs on any one inhalation. Thus,even at sealevel or afew. feet under the water approximately four-fifths of the usable oxygenineach inhalation is thrown away. At a depth of 99 feet air is drawninto the-lungs under a pressure of four atmospheres. Due to thecompressibility of air, there is thus four times as much availableoxygen in the drawn- ,in air as there would be at sea level, and,consequently,

type. The diver inhales from the breathing bag, through a one way checkvalve, returning the exhale-d air by way of another one Way check valveto the breathing bag through a canister containing a carbon dioxideabsorbent. The rate of oxygen consumed is thus equal to the rate ofmetabolic consumption of oxygen by the diver. As may be appreciated,this type is highly ethcient as all of the oxygen in the cylinder isutilized by the diver in breathing, with the unconsumed portion beingreturned to the breathing bag, the carbon dioxide being absorbed toprevent anoxia. With none of the oxygen being wasted a much smaller highpressure cylinder is needed.

The closed circuit type has the disadvantage in that it is notresponsive to pressure changes as the diver rises or descends. As thedepth increases the diver must reduce the pressure in the bag andreadjust the bag volume to are not possible without constant vigilanceon the part of the diver. Moreover, oxygen under a pressure of twoatmospheres for longer than 45 minutes has an adverse effect on thehuman body, and thus there is a danger of oxygen poisoning undersustained deep diving when using the closed circuit system.

Applicant has devised asemiclosed circuit to obtain the advantages ofthe above described systems and at the same time to eliminate thedisadvantage of the two systems. That is, the semiclosed circuitdescribed herein incorporates the automatic depth adjusting feature ofthe open circuit type which increases the efficiency thereof byrebreathing a substantial portion of the air exhaled, and admitting onlyenough air from a high pressure air reservoir to replenish the oxygenconsumed by the body. As has been pointed out above, the body uses onlyabout one-fifth of theoxygen taken into the lungs on any one inhalation.Therefore, it is possible to rebreath substantially four-fifths of theair exhaled, and only approximately one-fifth of an inhalation need benew air admitted to the system; provided, of course, that the carbondioxide is removed from the rebreathed air.

In the use of the semiclosed circuit, air, or oxygen mixed with an inertgas, is stored in cylinders under high pressure, as in the open circuit.This high pressure air is reduced to an intermediate pressure by a firststage reduction valve, again as in the open circuit. The air is obtainedfrom a breathing bag by the diver through a breathing bag, similar tothe closed circuit type. It is of great importance that the breathingbag be smaller than the divers lung capacity, for with each exhalationthe larger part of the exhaled air is returned to the breathing bag,with the remainder of the exhaled air being thrown away through anexhaust check valve. On the next inhalation the retained air will berebreathed along with a quantity of fresh air equal to the amount thrownaway. Of course, the exhaled air is passed through a carbon dioxideabsorbent in each cycle to remove the poisonous carbon dioxide.-

Since. the semiclosed circuit uses high pressure air, as does the opencircuit type, the chances of oxygen poison- :ing is absentyand sinceonly about one-fifth of new air is added to each'inhalation the timelimit for the use of the semiclosed circuit for a given capacity aircylinder is approximately five times that of the open circuit.

Further advantages of the semiclosed circuit will become more apparentin the following detailed description.

As the successful operation of the semiclosed circuit depends upon theexhausting of a portion of the exhaled air through the use of abreathing bag of smaller capacity than the lung capacity of the diver,it is seen that the maximum ba-g size that an individual can use will bedetermined by his lung capacity and the amount of the safety factordesired. That is, each lung full of air at the surface contains enoughoxygen for four additional breaths, before all of the oxygen is consumedfrom the original lung full. This means that for a diver to gain maximumefiiciency at the surface he would require a breathing bag that isfour-fifths of his lung capacity so that the other one-fifth of theexhaled air will exhaust through the exhaust valve. This would allow nosafety factor and he would be in danger of anoxia should he take shallowbreaths. If the diver then descends to a depth of 33 feet in the water,the pressure on the breathing bag and diver will double and twice asmuch new air will be admitted into the system on each inhalation ascompared to surface operation. That is, even though the volume of newair admitted will be the same the double pressure will double theconcentration of new air admitted to the breathing bag. With double theamount of new air, the amount of new oxygen'will be doubled inthenextinhalation, and since the metabolic consumpthe bag in expanded positionwill be somewhat less than four-fifths of the divers lung capacity. Asthe unde r water depth increases the second bellows 32 will becompressed allowing the breathing bag 13 to expand outwardly to agreater amount reducing the amount of old air expelled through theexhaust valve 26 and consequently less new air will be admitted throughvalve 28 on collapse of the breathing bag 13 on inhalation. A rigidstriker plate 36 is mounted on the movable end wall 21 of the breathingbag 13 to contact the valve stem 29 on collapse of the bag 13. As may beappreciated the second bellows 32' could be mounted on the outside ofthe movable end wall 21 of the breathing bag so that on expansion of thebreathing bag the bellows 32' will butt against the end wall 35 of thehousing 23 to limit the bag expansion, without altering the operation ofthe apparatus.

FIG. 4 illustrates yet another modification of the invention, employingthe principle discussed above. In this embodiment the valve stem 29 isadapted to be actuated by a first lever 37 pivoted about a support 38mounted on the housing 23. A second lever 39, pivoted about support 40also mounted on the housing 23, has a sealed bellows 41 mounted thereon,the bellows 41 having an end wall 42 adapted to push against the firstlever 37 when the breathing bag collapses so as to permit the strikingplate 36 to engage the second lever 39. As in the other modification thesealed bellows 41 is filled with air at atmospheric pressure. When theapparatus is used at sea level the bellows 41 will be fully expanded andthe breathing bag 13 may only partially collapse before the strikingplate 36 engages the second lever 39 to force the end wall 42 of thebellows 41 against the first lever 37 to open the valve 28. As the depthincreases the bellows 41 will be compressed and the breathing bag willbe allowed to collapse to a greater degree before the foregoingmanipulation of valve 28 occurs.

In the foregoing modification, it is obvious that the carbon dioxideremoving canister can be located in either the intake or outlet from theface work 11 with the same overall results.

It is to be understood that the forms of the invention, herewith shownand described, are to be taken as preferred examples of the same, andthat various changes in the size, shape and arrangement of parts may beresorted to, without departing from the spirit of the invention, or thescope of the attached claims.

Having thus described the invention, I claim:

1. In an underwater breathing apparatus, a collapsible breathing baghaving opposed end surfaces, port means in the bag for use in connectingthe bag to breathing apparatus, said end surfaces adapted to berelatively positioned adjacent each other on contraction of said bag andaway from each other on expansion of said bag, one of said end surfaceshaving a valve port formed therethrough, a valve having a valve stemextending through said port into said bag, a sealed bellows mounted onthe inside surface of the other end, said bellows being adapted tocontact said valve stem on contraction of said bag.

2. In a breathing apparatus for use in underwater diving, a collapsiblebreathing bag being adapted to expand and contract through a limitedvolumetric change and having opposed ends adapted to be relativelypositioned adjacent and then away from each other upon contraction andexpansion of said bag, port means in the bag for use in connecting thebag to breathing apparatus, one of said ends having a valve port formedtherethrough, a valve having a valve stem extending through said valveport into said bag, lever means mounted in said bag adapted to beengaged by the other end of said bag upon collapse thereof, and meanscontrolling and adjusting said limited volumetric change in directrelation to the underwater depth of said bag and including a sealedbellows attached to said lever means to engage said valve stem uponengagement of and actuation of said lever means by said other end ofsaid bag.

3. In a breathing apparatus for underwater diving, a circulating systemcomprising a mouthpiece, means for absorbing carbon dioxide, acollapsible breathing bag being adapted to expand and contract through alimited volumetric change and having an expanded volume smaller than thevolume of air breathed during one inhalation of the diver using saidbag, first tube means connecting said mouthpiece to said carbon dioxideabsorbing means, second tube means connecting said carbon dioxideabsorbing means to said breathing bag, third tube means connecting saidmouthpiece to said breathing bag, an exhaust check valve in saidbreathing bag, an air storage cylinder, means connecting said cylinderto said system, a normally closed demand valve in said last-named means,said demand valve being operable by said breathing bag upon collapse ofsaid bag to open to permit air from said cylinder to enter saidcirculating system, and pressure sensitive means for controlling andadjusting said limited volumetric change in direct relation to theunderwater depth of said device.

4. A breathing apparatus for underwater diving comprising a mouthpiece,means for absorbing carbon dioxide, a collapsible breathing bag havingopposed end surfaces adapted to be relatively positioned adjacent eachother on contraction of said bag and away from each other on expansionof said bag and having an expanded volume smaller than the volume of airbreathed during one inhalation of the diver using said bag, first tubemeans connecting said mouthpiece to said carbon dioxide absorbing means,second tube means connecting said carbon dioxide absorbing means to saidbreathing bag, third tube means connecting said mouthpiece to saidbreathing bag, one of said opposed end surfaces of said bag having avalve port formed therethrough, a valve having a valve stem extendingthrough said port into said bag, an air storage tank, means connectingsaid cylinder to said last named valve, a sealed bellows mountedinteriorly of said bag on the other opposed end surface, said bellowsbeing adapted to contact said valve stem on contraction of said bagwhereby said last named valve is actuated to admit air from said aircylinder into said bag.

5. A breathing apparatus for underwater diving comprising a mouthpiece,means for absorbing carbon dioxide, a housing member, a collapsiblebreathing bag mounted inside and on one wall of said housing member andhaving an end movable toward and away from said one wall on contractionand expansion of said bag said bag being adapted to expand and contractthrough a limited volumetric change; and having a maximum expandedvolume smaller than the volume of air breathed during one inhalation ofthe diver using said bag, first tube means connecting said mouthpiece tosaid carbon dioxide absorbing means, second tube means connecting saidcarbon dioxide absorbing means to said breathing bag, third tube meansconnecting said mouthpiece to said breathing bag, an exhaust check valvein said breathing bag, said one housing member wall having a valve portformed therethrough, a valve having avalve stern extending through saidvalve port into said bag, an air storage cylinder, means connecting saidcylinder to said last named valve, said end of said bag being adapted toengage said valve stem upon contraction of said bag to admit air fromsaid cylinder to said bag, a pressure sensitive means for-controllingand adjusting said limited volumetric change in direct relation to theunderwater depth of said bag and including a sealed bellows mounted onan inside wall of said housing member opposite said one wall.

6. A breathing apparatus for underwater diving comprising a mouthpiece,means for absorbing carbon dioxide, a collapsible breathing bag beingadapted to expand and contract through a limited volumetric change andhaving opposed end surfaces adapted to be relatively positioned adjacenteach other on contraction of said bag and away 7 from each other onexpansion, said bag having a maximum expanded volume smaller than thevolume of air breathed during one inhalation of the diver using saidbag, first tube means connecting said mouthpiece to said carbon dioxideabsorbing means, second tube means connecting said carbon dioxideabsorbing means to said breathing bag, third tube means connecting saidmouthpiece to said breathing bag, an exhaust check valve in saidbreathing bag, one of said opposed end surfaces of said bag having avalve port formed therethrough, a valve. having a valve stem extendingthrough said port into said bag, an air storage tank, means connectingsaid cylinder to said last-named valve, lever means mounted in said bagadapted to be engaged by the other end of said bag upon collapsethereof, and'pressure sensitive means including a sealed bellowsattached to said lever means for controlling and adjusting said limitedvolumetric change inidireet relation to the underwater depth ofsaidbagfwhereby said lever means Will-engage said valve stem uponengagement of-and actuation of said lever means References Citedin thefile of this patent UNITED STATES PATENTS 2,596,178 Seeler May- 13, 19522,732,840 De Sanctis Jan. 31, 1956 2,766,753,. K h' Oct. 16, 1956'2,900,97 Marsh Aug. 25, 1959 FQREIG N PATENTS Great Britain July 13V,1955

